Many integrated circuits include a variety of different components or logic blocks, some of which can be enabled at all times, others of which may periodically be enabled for activity and then placed into a low power mode. Further, the integrated circuit itself may at times be placed into a low power mode to reduce power consumption, particularly in a portable device.
Some integrated circuits include an on-chip voltage regulator (or are coupled to an off-chip voltage regulator). In either case, different control mechanisms for the voltage regulator may be used to maintain appropriate voltage levels depending on an activity state of the integrated circuit. However, switching between the different modes can be a relatively complex and time consuming event.